Solvent extraction method is a commonly used method to extract the active ingredients of traditional Chinese herbal medicine. Based on whether heating is applied, the extract method is divided into two types: cold extraction method and hot extraction method. The cold extraction method further includes impregnation method and percolation method, and is suitable for the extraction of the active ingredients that are unstable to heat. The cold extraction takes a long time and uses a large amount of solvent, and the extraction efficiency is low. The hot extraction method further includes boiling method, reflux method, and continuous extraction method, suitable for the extraction of heat-stable active ingredients. The reflux method is an important hot extraction method, but it takes a long time, and the active ingredients that are unstable to heat are easily decomposed and destroyed during the extraction. Fresh solvent is required for each batch. It is not suitable for continuous production. New extraction methods, such as supercritical fluid extraction, ultrasonic extraction and microwave-assisted extraction, have emerged, but these new extraction methods require expensive equipment and large investment and are not suitable for large scale production.
Common methods for separation and purification of active ingredients of traditional Chinese herbal medicine include extraction, precipitation, salting out, dialysis, crystallization, fractionation, etc. In recent years, new methods, such as supercritical fluid extraction, membrane separation, ultrafine pulverization technology, flocculation separation technology, semi-bionic extraction, ultrasonic extraction, cyclone extraction, pressurized counter-current extraction, enzymatic extract, macroporous resin adsorption, ultrafiltration, molecular distillation, have been used to separate and purify the active ingredients. Based on the nature of the active ingredients to be purified and the production need, one or two purification methods may be combined. For example, in a precipitation method, a reagent is added to an herbal medicine extract solution to produce a precipitate to either obtain an active ingredient or remove impurities. Water extracting and alcohol precipitation method or alcohol extraction and water precipitation method is often used to purify the active ingredients. After a reagent is added to the herbal medicine extract solution, the mixture was centrifuged and filtered. The extraction device and container are then cleaned for the next batch. The extraction operation is not continuous, and the active ingredient extract yield is low. There is a need for a continuous high efficiency herbal medicine extract method.